1. Field of the Invention
The present invention relates to a package for a semiconductor device having a mold frame and a production method thereof.
2. Description of the Related Art
Generally, in a resin-sealed semiconductor device, a semiconductor chip is mounted on a chip-mounting portion of a lead frame, and the semiconductor chip is electrically connected to leads by wires, and thereafter, the semiconductor chip is sealed by sealing resin.
On the contrary to the above, there is a package known as a pre-molded package which has a pre-molded portion having a recessed chip-mounting portion in an insert molding process in which the lead frame is inserted. In the package, a semiconductor chip is mounted on the chip-mounting portion, and the semiconductor chip is electrically connected to a wiring pattern provided around the chip-mounting portion, by wires, and thereafter, the chip-mounting portion is sealed by a lid to obtain a semiconductor device.
In recent years, the latter type of simple packages (i.e., pre-molded packages) have been used for various purposes owing to an enhanced airtightness due to an improvement of a passivation film of the semiconductor chip proper or an adhesive to seal the lid of the molded package.
FIG. 11 shows a schematic sectional view of a package 10 described above as a pre-molded package. 12 designates a lead frame, and 14 designates a molded portion. As shown in the drawing, the package in which the lead frame 12 and the molded portion 14 are integrated in advance is provided. A semiconductor chip 18 is mounted on a recessed chip-mounting portion 16. The semiconductor chip 18 is electrically connected to the lead frame 12 by wires 20. A lid 22 is cemented to the molded portion 14 by an adhesive 15 to cover the chip-mounting portion 16 so as to seal the semiconductor chip 18. Thus, the package can be used as a DIP type or gull-wing type semiconductor device.
However, a known package using the lead frame as described above has problems as follows.
The package is simple in structure, but is complex in the production process since after molding the molded portion 14 by a transfer molding as in a conventional resin-sealed semiconductor device, it is essential to remove a dam bar (not shown) which is provided to prevent resin from flowing out between the leads, and to remove any resin flash which has reached the dam bar between the leads.